Sound reproduction



June 25, 1940. H. J. HAsBRoucmuR 2,205,528

soUND REPRoDUcTIoN l Filed Feb. 5, 1935 AM P.

INVENTOR ATTORNEY Hal-nld Jansn Haslllnllnktk.

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Patented June 25, 1940 UNITED STATES PAENTJ OFFICE SOUND REPRODUCTION yporation of Delaware Application February 5, 1935, serial No. 5,014

2 Claims.

This invention relates to the reproduction of sound from records andparticularly tothe reproduction cf sound from film records of the noisereduction type wherein the photographic v positive print is transparentsubstantially only in portions corresponding to the sound modulations,any unmodulated transparent portion of the sound track beingsubstantially absent, thereby preventing ground noises in theunmodulated portion.

A pioneer disclosure in the art of reproducing sound from records of thenoise reduction type just mentioned is disclosed and claimed in U. S.patent to Adsit No. 1,291,702, patented January 2l, 1919. As disclosedin this patent, the record to be reproduced has opposite components ofthe recording appearing in separate longitudinal portions of the soundtrack, these portions lying on opposite sides of the center line of thesound track. In other words, the displacements of the galvanometermirror in one direction from its position of rest are recorded on oneside of the center line and the displacements of the galvanometer mirrorin the opposite direction are recorded on the opposite side of the sameline.

As disclosed in Adsit Patent 1,291,702, separate light beams areprojected through the separate sound track portions to produce currentswhich are combined in a push-pull circuit to reproduce the sound. Toavoid distortion in reproduction, each record portion should modulateits own light beam and not the other, in order that current from the twomodulated light beams may correspond to the separate record portions,whereby the actual sound is accurately reproduced. There may be severalfactors which cause distortion in reproduction such as the drift of thegalvanometer mirror from its center position, lateral weaving of the lmin the recording machine, film shrinkage, displacement of negative andpositive records in the printing machine, lateral weaving of thepositive lm in the reproducing machine, and maladjustment of thescanning light and light sensitive cell with respect to the sound track.

Although the record which I provide differs from the type. used in theAdsit system mentioned above, by having the opposite components orgalvanometer displacements separated on opposite sid-es of the centerline, which of itself aids in the elimination of distortion, the presentinvention provides a reproducing system, for

double sound track records, which reduces to a;

minimum the above mentioned factors pertinent to reproduction whichcause distortion of the (Cl. 17a-100.3)I

reproduced sound. In Adsit, two light sensitive devices, each receivinglight from one track component, are placed adjacent to the sound trackportion of the film. vThe present invention contemplates separating thefilm from the light sensitive devices by lan optical system whichpreferably magnies the sound track thus providing a greater separationbetween the two images of the sound track components, and a greaterlatitude for adjustment and operation as above described. The inventionfurther contemplates a reproducing system readily convertible toaccommodate either records having a double track or records having asingle track.

The features of the reproducing apparatus will be more fully understoodby referring to the following description read in conjunction with theaccompanying drawing in which:

Figs. l and 2 are sections of lm having two modifications of thepush-pull type of record.

Fig. 3 is a section of lm having a single track type of record thereon.

Fig. 4 is a diagrammatic drawing of a reproducing system adaptable foreither a single track or push-pull type of record,v this system employ.-ing photo-electric cells, and

Fig. 5 is a second modication of a reproducing system employing aselenium cell as well as being adaptable to either the push-pull orsingle track record.

Referring now to Figs. l and 2 showing film sections, the sound trackportions 29 have two tracks each madelup of modulations 3l and 32 inFig. l and modulations 4I and 42 in Fig. 2, these records having twotracks separated along parallel base lines. These records may beproduced with the recording systems disclosed and claimed in myco-pending application S. N. 3,239 filed Jan, 24, 1935. Each track 3l,32, 4| and 42 corresponds to a certain displacement of the 40galvanometer mirror in a particular direction and for properreproduction the beam of light modulated with each track must be keptseparate and made to eiiect its own particular light sensitive device.

The ilm section 5 shown in Fig. 3 is of the single track type withpicture portion 6, sound track portion l and modulations 9. With thistype of track only a single photo-sensitive element is required, theelement being aiected solely by the modulations since at the time of nosound, no light reaches the element.

Referring now to Fig. 4 which illustrates a reproducing system suitablefor any oi the sound record types above described, a lamp I2 ismaintained at a constant intensity from an energizing source I3 undercontrol ofa rheostat I4. The light rays from lamp I2 are collected witha lens system I6, projected on aperture plate I1, the aperture thereofbeing focused upon the sound track portion of lm I5 by lenses I8. Theemergent light from the nlm is projected by lens unit 20 upon a V-typemirror 22, which divides the light beam into two portions, one of whichimpinges upon a light to current translator such as photo-electric cell23 and the other upon another light to current translator such asphotoelectric cell 2li. These cells are energized in a circuit having anenergy source 26, a switch 27 and the primary of a transformer 28. Theoutput of the transformer 28 is fed to an amplier 3l connected to acurrent to sound translator such as a reproducing unit 3U.

In operating the above system the lamp l2 is energized and the film I5moved at the proper speed, say [eet per minute. li either type of nlmshown in lligs. l and 2 is being reproduced the lens system andreflector 22 is so adjusted that the light through one track ofmodulations is impinged upon one of the photo-electric cells and theight through the other track is impinged upon the other photo-electriccell. Since there is s. definite separation between the two tracks cimodulations a certain amount ol iilm weaving may occur withoutpermitting either light beam to impinge upon the wrong cell. For therepro-- duction ci the type of records of Figs. l and 2, tle r yitch 2?is thrown in upward position, which connects the cells 23 and 2li in apush-pull relationship with. the transformer 28; that is, the commonanc-de connection through energy source 25 ls connected to the midpointof the prin'iary oi? the transformer 28 while the cathodes of the celsare connected to respective terminals of the primary. Each modulation inthe separate tracks affects one particular cell and since thesemodulations are longitudinally displaced along the sound track portion,each cell is actuated successively in accordance with the modulat-ionsor transparent portions in each track. The current variations set up intransformer 2d are cmplined in the ampliiicr 3l and reproduced at Sli.It is to be understood that the lens unit 2li may magnify the lightimages and thus provide a greater separation between the tracks, at themirror 22, thus decreasing the possibility ci a light beam impingingupon the wrong cell.

To reproduce film of the type shown in Fig. 3 or any other single trackrecord ci either variable area or density, it is only necessary tomanipulate the switch E? from its upward position to its lower position.This manipulation connects the cells 23 and 24 in a parallerelationship, that is, the anodes now connected. through the source 25to the upper terminal of the primary oi the transformer 28 while thecathodes are now connected together to the lower terminal of theprimary. With this connection the light falling on either cell willsupplement the light falling on the other. this system operating ineiect as a single cell arrangement. In this circuit arrangement,therefore, it is only necessary to throw the switch to either of itsoperating positions when records of different types are introduced inthe system to efficiently reproduce them.

Referring now to Fig. 5 showing another modification of the reproducingsystem, the drawing shows the same light source, lens system and film asshown in Fig. 4 except in perspective. The systems diier, however, inthe use of dinerent types of optical systems between the film andphoto-sensitive device which in this case is a selenium. cell. Thisoptical system comprises a cylindrical lens 34 and a spherical lens 35which function to project an enlarged image of the sound track upon theselenium cell 36, this cell being of the type disclosed in U. S. PatentNo. 1,948,766 patented February 27th, 1934. The cell is a modied cellhaving a vertical trace 33 which divides the cell into three sections,thus adapting it for use in a push-pull system connected in the samemanner as the two photoelectric cells of Fig. 4. The trace 33corresponds to the forward edge of the V-type mirror 22, in providing adividing line between the two sound track images.

The operation of the system in Fig. 5 is substantially identical withthat of Fig. 4, the optical system, including the cylindrical lens 34and the spherical lens 35 serving to elongate and widen the image of thesound track upon the grid of the selenium cell 33 for the purpose ofproviding a greater latitude for film weaving and also to produce a moreefcient cell response. 1t has been found that if a certain light quantumfalling on selenium cell 35 is reduced in intensity and spread over theentire grid of the cell, that the efficiency of the cell will beincreased and distortion decreased.

The switch arrangement 2T' is operated in the same manner as in 4 foraccommodating either a single track or a double track nlm, that is, withthe switch thrown in its upward position, the sections of the seleniumcell 33 are connected in a push-pull relationship while with the switchin its lower position a parallel connection is made to the transformer28. It has been found that the above optical systems and arrangements ofphoto sensitive elements eliminate or reduce many of the faults ofreproduction listed above.

What is claimed is:

1. In a system for reproducing sound, a selenium cell having anelectrode and a parol electrodes interdigitated with said rst electrodeand separated by a trace, means for projecting a modulated light beam tocompletely cover at all times one member of said pair and a portion ofsaid first electrode, and a second modulated light beam to completelycover at all times the other member of said pair and another portion ofsaid first eectrode, and a common circuit connected to all oi saidelectrodes.

In a sound reproducing system, a sound recording, a selenium cell havingthree electrode portions, means for passing a light beam through saidsound recording to said seenium cell, and an optical system including acylindrical lens and a spherical lens in a series relationship betweensaid sound recording and said selenium cell for increasing substantiallythe whole oi the image of said sound recording to a size comparable withsaid selenium cell, and an output circuit connested to said electrodes.

HAROLD JANSEN HASBROUCK, JR.

